1. Field of the Invention
The present invention relates to cleaning methods and compositions for debonding and/or cleaning debonded substrates, such as substrates used in temporary wafer bonding processes.
2. Description of Related Art
During the manufacture of three-dimensional (3-D) integrated semiconductor microcircuits, it is often necessary to temporarily bond a device wafer to a carrier wafer with an adhesive so that the device wafer can undergo grinding, thinning, photolithography, chemical vapor deposition (CVD), and/or other processes. After all the necessary processing steps are completed, the device wafer is then separated, or debonded, from the carrier wafer. Debonding of a device wafer from the carrier following backside processing can be typically performed by various processes such as:
(1) Chemical—The bonded wafer stack is immersed in, or sprayed with, a solvent or chemical agent to dissolve or decompose the bonding material.
(2) Photodecomposition—The bonded wafer stack is irradiated with a light source through a transparent carrier to photodecompose the bonding material adjacent to the carrier.
(3) Thermomechanical—The bonded wafer stack is heated above the softening temperature of the bonding material, and the device wafer is then slid, pulled, or peeled away from the carrier while being supported with a full-wafer holding chuck.
(4) Thermodecomposition—The bonded wafer stack is heated above the decomposition temperature of the bonding material, causing it to volatilize and lose adhesion to the device wafer and carrier.
Regardless of the method, residual bonding material must generally be cleaned from the device wafer prior to the next processing step. Furthermore, sometimes-expensive carrier wafers must be cleaned for reuse. Conventional hydrocarbon solvents that dissolve the temporary adhesives do not clean effectively because they leave too much residue, as do conventional solvents used for chemical separation of the substrates in the first place. Strong acidic or alkaline solutions such as concentrated sulfuric acid/hydrogen peroxide (Nano-Strip or Piranha solution) and RCA cleaning solutions may effectively clean the wafers, but they are corrosive and can attack metallic circuits or pads. Thus, there remains a need in the art for improved cleaning solutions for separating and cleaning temporarily bonded substrates.